The subject matter described herein relates to electronic computing, storage systems, and more particularly to tape drive position control.
Many magnetic tape storage systems implement a recording technology referred to as “linear recording” technology. Linear recording tape systems record information in multiple parallel tracks that extend in the direction of the length of the tape. Most, linear recording systems use a stationary tape head operating on tape that is driven past the tape head at a controlled speed. The tape head may employ multiple read/write elements that can operate simultaneously on the tape.
Continuing advances in magnetic storage technology provide for constantly increasing data storage densities. The more tracks that can be fit across the width of a tape, the more information that can be stored on a tape. Thus, there is a push to increase the number of tracks across the width of a tape and to reduce the width of each track. Increasing the number of tracks or reducing the width of a track makes accurate positioning of read/write elements, and issues of tape wander more important.
Servo control systems employ information or patterns recorded along a track of the tape to accurately position read/write elements relative to data on the tape. Servo patterns on a tape may include a characteristic that changes across the width of the tape. The servo information can be used to accurately position heads relative to the length of the tape (e.g., when searching for a desired position along the length of the tape, such as the start of a file) as well as relative to the width of the tape. Thus, as a servo element passes over the servo track, lateral position can be determined.
Servo control systems commonly implemented a sampling routine to collect position information from the servo patterns on a tape. In some instances, the sampling process can create images or aliases of signals from structural resonances. These images or aliases can cause undesirable instability and oscillations in the control routine implemented by the servo control system, thereby interfering with the control system's ability to position correctly the tape head with respect to that tape.